Photosynthesis: An Overview

Let’s Make Our Own Food! Plants trap sunlight and store it for the organelles to use later in the form of food. The process of trapping light and converting it into food is called photosynthesis.

Overview of Photosynthesis Scientists describe the reactions of photosynthesis in two phases: Light - Dependent Reactions Takes place in the thylakoid membrane 2. Light – Independent Reactions Takes place in the stroma So even if it is cloudy or dark the plants are still working to make food!

Light-Dependent Reactions Need sunlight! The energy from light-dependent reactions is used in the light- INDEPENDENT reactions!

Light-Independent Reactions Do NOT need light. These reactions are fueled by energy from the light-dependent reactions. They produce stored energy/food for the plant.

The Photosynthesis Equation

Chloroplasts Photosynthesis takes place inside organelles called chloroplasts. In the chloroplasts, there are membranes that have pigments that absorb light. What color do you think they are? The pigment is called chlorophyll.

Chloroplasts Pigments are located in the thylakoid membranes. The fluid portion outside of the thylakoids is known as the stroma.

Chloroplasts

Photosynthesis The chlorophyll absorbs sunlight and uses it t o react water with carbon dioxide. The reaction produces sugars (glucose) and oxygen. We breathe the oxygen made from photosynthesis!

Factors Affecting Photosynthesis Among the most important factors that affect photosynthesis are temperature, light intensity, and the availability of water.

Temperature, Light, and Water The reactions of photosynthesis are made possible by enzymes that function best between 0°C and 35°C. Temperatures above or below this range may affect those enzymes, slowing down the rate of photosynthesis or stopping it entirely.

Temperature, Light, and Water High light intensity increases the rate of photosynthesis. After the light intensity reaches a certain level, however, the plant reaches its maximum rate of photosynthesis, as is seen in the graph.

Temperature, Light, and Water Because water is one of the raw materials in photosynthesis, a shortage of water can slow or even stop photosynthesis. Water loss can also damage plant tissues.

Temperature, Light, and Water Plants that live in dry conditions often have waxy coatings on their leaves to reduce water loss. They may also have biochemical adaptations that make photosynthesis more efficient under dry conditions.